Journal Article

Effects of differing withdrawal times from ractopamine hydrochloride on residue concentrations of beef muscle, adipose tissue, rendered tallow, and large intestine

Prenni, Jessica E., Geornaras, Ifigenia, Delmore, Robert J., Davis, Haley E., Lindstrom, Valerie, Chaparro, Jacqueline M., Engle, Terry E., Nair, Mahesh N., Belk, Keith E.

2020

Overview

Ractopamine hydrochloride (RAC) is a beta-agonist approved by the U.S. Food and Drug Administration (FDA) as a medicated feed ingredient for cattle during the final days of finishing to improve feed efficiency and growth. Maximum residue limits and U.S. FDA residue tolerances for target tissues have defined management practices around RAC usage in the U.S. However, many countries have adopted zero tolerance policies and testing of off-target tissues, presenting a major challenge for international export. Therefore, the objective this study was to determine the necessary withdrawal time among cattle group-fed RAC to achieve residue concentrations below tolerance levels in muscle and off-target tissues. Specifically, both total and parent RAC residues were quantified in muscle, adipose tissue, rendered tallow, and large intestines from animals group-fed RAC and subjected to withdrawal 2, 4, or 7 days before harvest. Ractopamine (parent and total) residues were below the assay limit of detection (< 0.12 ng/g) in all muscle and adipose tissue samples from animals in control groups (no RAC). However, RAC residues were detectable, but below the limit of quantitation, in 40% of tallow and 17% of large intestine samples from control animals. As expected, mean RAC residue concentrations in muscle, adipose tissue, and large intestine samples decreased ( P < 0.05) as the RAC withdrawal duration (days) was extended. Irrespective of RAC withdrawal duration, mean parent RAC residue concentrations in muscle, adipose tissue, and large intestine ranged from 0.33 to 0.76 ng/g, 0.16 to 0.26 ng/g, 3.97 to 7.44 ng/g, respectively and all tallow samples were > 0.14 ng/g (detectable but below the limit of quantitation). Results of this study provide a baseline for the development of management protocol recommendations associated with withdrawal following group-feeding of RAC to beef cattle in countries that allow RAC use and intend to export to global markets which may be subject to zero tolerance policies and off-target tissue testing.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: Adipose tissue / Adrenergic beta blockers / Adrenergic beta-antagonists / Animal sciences / Animal tissues / Animals / Beef / Beef cattle / Biology and Life Sciences / Body fat / Cattle / Cattle feeds / Design / Dosage and administration / Drug dosages / Drug Residues - analysis / Drug therapy / Drug withdrawal / Efficiency / Exports / Fats - chemistry / FDA approval / Feed conversion / Feed efficiency / Feeds / Food / Global marketing / Horticulture / Intestine / Intestine, Large - chemistry / Landscape architecture / Large intestine / Least-Squares Analysis / Limit of Detection / Medicated feeds / Medicine and Health Sciences / Muscles / Muscles - chemistry / Phenethylamines - analysis / Phenethylamines - pharmacology / Physical Sciences / Physiological aspects / Policies / Quality standards / Quantitation / Ractopamine hydrochloride / Red Meat - analysis / Research and Analysis Methods / Residues / Tolerances / Veterinary drugs / Veterinary medicine / Zero tolerance